Today, off-highway trucks are used to mine oil sands and oil sands overburden or cover materials. The oil sands are then processed to separate the sand, water and oil which make up the mined oil sands. The mining of oil sand is relatively straightforward, although the complexity of the mining is increased by 1) the natural cohesive characteristics of oil sand, 2) the amount of oil sand being mined and 3) the environmental conditions under which it is mined.
The composition of oil sand and oil sand overburden/cover material is by its very nature extremely oily and sticky. The composition of mined oil sand is; 1) a grain of sand, 2) surrounded by or encapsulated by moisture/water and 3) oil which encapsulates and surrounds both the grain of sand and the water. To process oil sands in order to separate and recover the oil, heat is applied to the grains of oil sand. The water encapsulating the grains of sand turns to steam, which frees the oil from the sand grains. The end result of this process being 1) steam, 2) clean (white) sand and, 3) oil.
In its natural state, grains of oil sand are extremely sticky and they freely cling to each other. This can result in a buildup of oil sand on surfaces that contact the oil sands. For example, walking around on natural oil sands will quickly result in the soles of a person's shoes building up with layers of oil sand that can buildup to 8 to 10 mm thick.
This same sort of buildup happens in truck bodies. A common condition that occurs during the use of truck bodies is the buildup of “carryback.” As successive loads are hauled, sticky hauled material begins to incrementally buildup in the interior of truck bodies with each load until the body retains a significant amount of material between successive loads “carryback”. Experience has shown that initial load carryback begins in those areas of a truck body where intersecting walls of a truck body meet.
This buildup of material or “carryback” is significant for very sticky materials such as oil sand. The characteristics of oil sand sticking together and coagulate are exacerbated as oil sand in its natural state is disturbed by the oil sand mining process. With this sort of material, the buildup of carryback happens quickly and it is significant. This significant carryback reduces the effective capacity of the truck body and reduces the efficiency of the off-highway truck and the overall mining operation.
Oil sands loading shovels weigh in at 1450 to 1800 tons and off-highway trucks weigh in at 550 to 600 tons. Operating this equipment over oils sand deposits as oil sands are mined subjects the oil sand deposits to massive compressive forces. As loading shovel buckets dig into the oil sands and load or “drop” 100 tons at a time into off-highway truck bodies, the oil sands are further compressed in off-highway truck bodies. Also, oil sands hauled in an off-highway truck body further compact as off-highway trucks navigate the oil sand mine haul roads to their destination by vibrating the load, causing settling of the oil sand load in the off-highway truck body. By the time an off-highway truck reaches its destination, the shaking and resulting settling of the oil sand load results in the hauled oil sands amalgamating into an almost a solid packed mass.
The circumstances of oil sands mining and hauling, with the cohesive coagulating characteristics of the hauled oil sand results in the hauled oil sands dumping from the truck body as a solid mass or “loaf.” As loads of oil sand “loafs” exit truck bodies, the truck chassis itself is subjected to extreme ‘jolts,’ resulting in severe truck driver discomfort. Drivers of trucks hauling oil sand “loafs” are often exposed to extreme ‘whole body vibration’ as oil sand “loafs” are dumped.
For the average individual, the shear amount of oil sands being mined today is almost beyond comprehension. Today, about every two (2) tons of oil sands mined produces about one (1) barrel of oil. Current production of oil from oil sands surface mining operations alone in the Northern Alberta Region of Canada is about 750,000 barrels of oil a day, which translates to the daily mining of one and a half million tons of oil producing oil sands. This number does not include any oil sands overburden/cover materials that must also be mined to expose the oil sands.
By comparison, the Hoover Dam spanning the Colorado River required 3,250,000 cu. yards (2.6 million cu. m.) of concrete, which has been compared to the amount of concrete in a 16-ft. wide (4.9 m) highway between Pensacola, Fla., and Seattle, Wash. Putting this into perspective, enough oil bearing sands material is mined/hauled today to recreate a new Hoover Dam about every four days. Mining oils sands is a massive endeavor.
The environmental conditions for mining oil sands are extremely challenging. Today, the bulk of oil sands mining occurs in Northern Alberta, Canada. In this region of the world, temperatures in the winter months can get very cold, approaching minus 40 degrees Celsius (about −40° Fahrenheit). But in the summer months, temperatures often exceed 35 degrees Celsius (+95° Fahrenheit), resulting in the oils sands having a semi-fluid, sticky and goby consistency. Although the oil sands are very oily in composition, as they are mined they tend to re-solidify, in a truck body, to a very firm single mass (“loaf”), which invariably may tend to stick to the inner surface of the truck body. In either climate, though, as loads of oil sands material are dumped from a truck body, an oils sands ‘loaf’ is created. And, yet a clean release of the material from the inner surface of a truck body can be problematic. Transporting oil sands material is virtually unknown outside the localized mining of oil sands.